根据公共键/值对重新排列对象数组

Question

我有以下对象数组：

[
   {
     message: 'This is a test',
     from_user_id: 123,
     to_user_id: 567
   },
   {
     message: 'Another test.',
     from_user_id: 123,
     to_user_id: 567
   },
   {
     message: 'A third test.',
     from_user_id: '456',
     to_user_id: 567
   }
]

如何构造一个新的对象数组，其中最外面的对象键基于原始数组中找到的公共键？

这就是我所追求的：

[
  {
    123: [
      {
        message: 'This is a test',
        from_user_id: 123,
        to_user_id: 567
      },
      {
        message: 'Another test.',
        from_user_id: 123,
        to_user_id: 567
      }
    ]
  },
  {
    456: [
      {
        message: 'A third test.',
        from_user_id: '456',
        to_user_id: 567
      }
    ]
  }
]

请注意，在第一个数组中，用户 ID123显示在两个对象中。这将是新数组中第一个元素的对象键。

Answer 1

您可以使用一个对象并将from_user_id属性作为该对象的键。然后将实际对象推送到组中。groups为了获得最终结果，迭代任意组的键并构建一个新对象。

var data = [{ message: 'This is a test', from_user_id: 123, to_user_id: 567 }, { message: 'Another test.', from_user_id: 123, to_user_id: 567 }, { message: 'A third test.', from_user_id: '456', to_user_id: 567 }],
    groups = Object.create(null),
    result;

data.forEach(function (a) {
    groups[a.from_user_id] = groups[a.from_user_id] || [];
    groups[a.from_user_id].push(a);    
});

result = Object.keys(groups).map(function (k) {
    var temp = {};
    temp[k] = groups[k];
    return temp;
});

console.log(result);

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与单循环方法一起

var data = [{ message: 'This is a test', from_user_id: 123, to_user_id: 567 }, { message: 'Another test.', from_user_id: 123, to_user_id: 567 }, { message: 'A third test.', from_user_id: '456', to_user_id: 567 }],
    result = data.reduce(function (groups) {
        return function (r, a) {
            var temp = {};
            if (!groups[a.from_user_id]) {
                groups[a.from_user_id] = [];
                temp[a.from_user_id] = groups[a.from_user_id]; 
                r.push(temp);
            }
            groups[a.from_user_id].push(a);
            return r;
        };
    }(Object.create(null)), []);

console.log(result);

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